1. Field of the Invention
The present invention relates to a rotor for a dynamoelectric machine such as an automotive alternator, etc., and particularly relates to a bobbin output wire securing portion construction that engages an output wire of a rotor coil.
2. Description of the Related Art
In conventional automotive alternator rotors, a rotor coil is wound onto an insulating bobbin that is disposed between a pair of pole core bodies, and output wires that are led out from the wound portion of the rotor coil are held by an output wire securing portion that is disposed on a flange portion of the insulating bobbin so as to prevent winding collapse. These output wires are protected electrically by an insulating tube, pass through a groove that is disposed on the pole core body, and are connected to terminals that are disposed on slip rings. An excitation current is supplied to the rotor coil by means of the slip rings and brushes that are housed in a brush holder that is held by a bracket.
Generally, speed increasing ratios of automotive alternators are set so as to be high so as to achieve sufficient output even when rotational frequency is low in the engine that drives the alternator, and maximum rotational speeds can reach up to 18,000 rpm. Because of this, large centrifugal forces act on the output wires of the rotor. The rotational speeds of vehicle engines also vary depending on vehicle speed, electric loads, etc., generating rotational fluctuations in an internal-combustion engine. These changes in rotational speed act on the output wires of the rotor. Because stresses thereby act on the output wires repeatedly, one problem has been that the output wires are easily broken, reducing durability of the output wires.
In order to solve problems of this kind, in Patent Literature 1, for example, output wires of a rotor coil that are led out from an output wire securing portion are disposed so as to extend alongside a wall surface that is formed into a root portion between claw-shaped magnetic poles of a pole core body parallel to a central axis of a shaft. Because the length of the output wires can thereby be shortened, centrifugal force that acts on the output wires is reduced, making the output wires less likely to break and improving durability of the output wires.
Patent Literature 1: Japanese Patent Laid-Open No. 2001-37180 (Gazette)
Because automotive alternators are mounted in engine compartments, they must generate power in the high ambient temperatures of engine compartments, which are at approximately 100 degrees Celsius, and temperatures in the stator coil, etc., which is a heat-generating portion, may even reach 200 degrees Celsius. Thus, the insulating bobbin onto which the rotor coil is wound is prepared using a resin while taking into account insulation, heat resistance, cost, etc.
Now, in an automotive alternator according to Patent Literature 1, if large centrifugal forces occur at high temperatures, because the output wire securing portion of the insulating bobbin in particular is subjected to the centrifugal force that acts on the output wires in addition to the centrifugal force that acts on the output wire securing portion itself while being exposed to high temperatures, the output wire securing portion may also deform greatly. Thus, one problem has been that large stresses act on the output wires held by the output wire securing portion, giving rise to wire breakage in the output wires and reducing durability of the output wires.